This invention relates to rotating pumps or compressors of the scroll type and more particularly to reducing leakage of the fluid being compressed across the tips of the scroll wraps in a scroll compressor.
Scroll type compressors have been known, in principle, for several decades. In general, a scroll-type compressor or similar machine comprises a pair of mating scrolls, each of which has an involute spiral wrap of similar shape, mounted on respective base plates. Normally, one scroll is held fixed, and the other is movable, to orbit but not rotate, about the axis of the fixed scroll, being held by an Oldham ring or other anti-rotating structure. The walls of the two involute wraps define crescent-shaped volumes which become smaller and smaller and move from the outside to the center of the mating scrolls as the orbiting scroll revolves. A compressible fluid, such as a refrigerant gas, can be introduced at the periphery of the spiral wraps, and is compressed as it is moved under the orbiting motion of the device. The compressed fluid is then discharged at the center. By introducing a compressed fluid at the center and permitting its expansion to drive the devices, the scroll machine can be used as a motor.
The orbiting motion of the moving scroll means that at the tip of the scroll wrap of both the orbiting and the stationary scroll there is a convoluted interface across which the fluid being compressed can leak from the high pressure side to the low pressure side of these devices. To minimize leakage at the scroll tip the devices have been manufactured with extremely tight tolerances but it still has been found desirable to modify the tip to further reduce leakage. The standard type O-ring material placed in a slot in the scroll wrap tips has been unsatisfactory for a number of reasons, principally swelling of the material and consequent loss of spring rate such that the sealing effectiveness of the material is lost or the material disintegrates and inhibits the orbiting action of the movable scroll.
As proposed in the copending application Ser. No. 461,759 assigned to the common assignee of this application previously filed on the day of Jan. 8, 1990, a compound "C"-shaped cross section spring having an O-ring sealing core has been proposed as one method of reducing fluid leakage across the tip of the scroll wrap of the scroll compressor. For many applications, this type of scroll wrap tip seal works very effectively, however, for certain types of materials being compressed and for certain applications other leakage reducing means are preferred.